I think you should pull the shock off and reinstall the rubber bushings. The bushing should fit in the shock and have a small lip that protrudes on each side of it, there is often a steel "pipe" that goes through the bushing and through that "pipe" goes the mounting bolt or stud. It will be much easier to get the bushings reinstalled with the shocks off. If a lubricant is needed use something like Armor-all, petroleum by-products like grease or oil will deteriorate the rubber. The outer flat washer should be of a large enough diameter that the shock can not slide past it.